This invention relates to an engine control device for an internal combustion engine and more particularly to an arrangement for slowing the speed of an engine in response to an overheating condition and preventing of backfiring of the engine through its exhaust system when the slowing condition is initiated.
A wide variety of protective devices are provided for internal combustion engines such as spark ignited engines. For example, arrangements have been provided for sensing the operating temperature of the engine and for effecting a slowing of the engine in response to engine temperatures greater than a predetermined value. One popular way in which the engine speed is slowed in response to the sensing of an over temperature condition is by misfiring the spark plugs of the ignition system. Such misfiring will slow the engine speed. An example of an arrangement for slowing the engine under such conditions through misfiring of the spark plugs is disclosed in U.S. Pat. No. 4,459,951, entitled Overheat Preventing System For Internal Combustion Engines, issued July 17, 1984 in the name of Motoi Tobinaga et al. Although such arrangements have particular utility, most engine ignition systems include a spark advance mechanism whereby the time of firing of the spark plug is dependent upon a variety of engine running conditions including engine speed. However, when the engine is slowed by misfiring, the timing may be such that backfires might occur in the engine exhaust system. That is, the delayed timing of the firing of the spark plugs can cause hot gases to issue from the exhaust port of the engine and create a combustion characteristic in the exhaust system commonly known as backfiring or firing back. Such a condition is, obviously, undesirable.
It is, therefore, a principal object of this invention to provide an improved arrangement for protecting an engine in response to a dangerous condition and, at the same time, insuring that backfiring will not occur in the exhaust system of the engine in response to the slowing of the engine.
It is a further object of this invention to provide an improved arrangement for protecting an engine in response to an abnormal running condition and also insuring that backfiring will not occur in that event in the engine exhaust system.
It is a further object of this invention to provide an arrangement for slowing the speed of an engine when an overheating condition occurs and also for insuring that backfiring will not occur in the exhaust system due to the slowing of the speed of the engine.